The invention relates to a gas generator and especially a gas generator for an air bag, the generator includes a housing, which is open at two opposing end faces and a wall of the housing has at least one gas orifice, two cover elements for closing the end faces of the housing, a combustion chamber, arranged in the housing and having at least one outlet orifice, for receiving and burning gas-developing material ignitable by means of an ignition unit and at least one filter element, arranged in the housing and having several wire mesh mats, for cleaning the combustion gases flowing therethrough.
Known gas generators are mostly round generators, whose housing is composed of several parts, which, to some extent, make necessary relatively costly connection techniques and processes for connecting the individual housing parts. The filter elements necessary with gas generators, with which filter elements the combustion-gas flow is cleaned, must be formed into costly shapes (tube form, bowl form, cap form) because of the geometric structure of the round generators. Advantages with regard to the assembly of the individual housing parts are offered by a tubular gas generator, as is known for example from DE 39 14 690 C2. The known tubular gas generator has a cylindrical outer tube, which represents the housing of the gas generator and whose open end faces are closed by cover elements. A cylindrical inner tube of smaller diameter is arranged coaxially in the outer tube; this inner tube defines the combustion chamber, in which there is accommodated a gas-generating material ignitable by means of an ignition unit, and whence is provided with several gas outlet orifices in the tube wall. A filter element is located in the annular chamber between the inner tube and the outer tube, the filter element generally consisting of a plurality of layers of wire netting, steel wool and/or fibreglass. The combustion gas issuing from the gas outlet orifices through the filter elements, which take up solid and liquid or condensed combustion products, and issues cleaned by means of the gas orifices in the outer tube. The wire mesh filter elements are relatively rigid and resistant to bending, for which reason they can only be shaped to correspond to the annular chamber with great effort. In a round gas generator the woven filter mats are brought or wound into welded round shapes. Due to the necessity of having to adapt the filter elements to the geometric reality of of the gas generator housing by means of deformation, the manufacture of the known gas generators is very cost-intensive. Specifically, tubular and round gas generators cannot be, or can scarcely be adapted to the spatial factors due to their geometric shape predetermined by the tubular housing. In this respect there are limits to the use of such gas generators for motor vehicle air bags.